Infusion devices are typically used to deliver infusion media, such as medication, to patients. An implantable infusion device is designed to be implanted in a patient's body, to administer an infusion medium to the patient at a regulated dosage. An external infusion device is designed to be located outside of the patient's body and connected to the patient by a suitable catheter, tubing or the like, to administer an infusion medium into the patient's body.
Both implantable and external infusion devices may include one or more pump drive mechanisms for creating pumping forces to cause or help delivery of infusion media to the patients. Various types of pump drive mechanisms with electromagnetic drive devices have been developed for such infusion devices. Such pump drive devices typically include an electromagnetic actuator having an armature portion made of a magnetically conductive material. The armature interacts, electromagnetically, with an electrical coil housed in a coil cup made of magnetically conductive material. Such drive mechanisms include, for example, the drive mechanisms described in U.S. patent application entitled “Infusion Device and Driving Mechanism For Same,” Ser. No. 10/033,722, filed Dec. 27, 2001, by the owner of the present invention. Other pump drive mechanisms having electromagnetic armature-coil assemblies include, for example, those described in U.S. Pat. No. 4,594,058 to Fischell; U.S. Pat. No. 4,684,368 to Kenyon; U.S. Pat. No. 4,569,641 to Falk et al.; U.S. Pat. No. 4,568,250 to Falk, et al.; U.S. Pat. No. 4,636,150 to Falk, et al.; and U.S. Pat. No. 4,714,234 to Falk et al.
Pump drive mechanisms for infusion devices (including those referenced above) may include components, such as actuators, that come into direct contact with the infusion medium during normal operation. In such infusion devices, the chemical interaction of the infusion medium with materials used for such components may have an adverse effect on the patient to which the infusion medium is administered. The risk of such an adverse effect may be greater for implantable infusion devices, where components of an infusion pump may remain in contact with infusion medium over a prolonged period of time inside of an implanted device. For example, contact with the armature may cause leaching or other interactions of materials between the infusion medium and the armature. Such interactions may adversely alter the medical effect of the infusion medium on the patient. Prolonged contact may cause other detrimental effects, such as corrosion of the armature.
Pump drive mechanisms may be manufactured for use with a particular, known infusion medium, in which case, the effect (and prolonged effect) of direct contact of that particular infusion medium on components of the pump drive mechanism may be studied in advance. With such studies, the materials and components of the infusion pump may be selected and designed to be in contact with the infusion medium, yet, have a suitably benign effect on the patient. However, if the particular type of infusion medium is not known at the time of manufacture of the pump mechanism, for example, in the case in which a pump mechanism is being manufactured for multiple possible infusion uses, the ability to study effects on all possible infusion media may not be practical or possible. Accordingly, there is a demand in the industry for a pump mechanism and process that is suitable for multiple possible infusion uses.
In some contexts of use, the infusion device must be operable for an extended period with a limited power supply. For example, battery powered infusion devices may be implanted in or otherwise connected to patients, to deliver medication at controlled intervals over a prolonged period of time. A battery replacement in an implanted device may require surgery on the patient to remove and re-implant the device. Accordingly, there is a demand in the industry for infusion devices which make efficient use of power supplies and, thus, require fewer or no power supply replacements.
Because implantable infusion devices are designed to be implanted in the patient's body, the dimensions of such devices can have an impact on the determination of the location in the body at which a device may be implanted, the level of comfort of the implant patient and the external appearance of the implant site. Typically, a device with relatively small dimensions and, in particular, a relatively small thickness form factor, will provide greater flexibility in the choice of location in the patient's body to place the implant and will minimize patient discomfort and minimize noticeable protrusions at the implant site. Accordingly, there is a demand in the industry for minimizing the overall dimensions, and, in particular, the thickness dimension of implantable infusion device.